1. Field of the Invention
The invention concerns a specific configuration of multiple-conduit tubing, and a method of preforming this tubing for use with known body-care apparatus which include a hydraulic motor with a turbine, piston or membrane, operating with a liquid under pressure coming from a pump via a flexible tube to drive a working instrument, notably a toothbrush or to supply a spray nozzle by means of a by-pass valve.
2. Brief Description of the Prior Art
With apparatus of this type, it is generally advantageous to have not only a conduit for the water supply of the handpiece, but also a second exhaust conduit and for this reason it is known to use a double tube of plastic material having two juxtaposed conduits, which tube is available on the market, and which is then preformed so that when it is not used it takes the shape of a helix so as to reduce its bulk and avoid its becoming tangled. The double tube is made in a material which can be formed by the action of heat, notably, a synthetic resin, such as polyethylene based or nylon.
Preforming of the tube into a pipe has been carried out to date by means of a cylindrical support with a smooth surface on which the double tube is helically wound, the larger face or "larger side" applying naturally against the surface of the support whereas the turns apply against one another by the tube edge or "small side".
Then the assembly is heated for example in hot water at, in the case of polyethylene, a temperature of about 95.degree. C. for 1 to 2 minutes and then the tube is immersed in cold water, these figures of course depending on the type of plastic used. One thus obtains a preforming of the tube in a helix or coil to which the tube returns automatically when it is not submitted to a traction. There are also known casings of hydraulic body care apparatus which have a suitable recess in which said tube in helical configuration may be stored.
However, if this preforming has been carried out in such a manner that the joining line between the axes of the two conduits is parallel to the axis of the cylindrical support during the winding so that the length of the helix thus formed by the preformed tube is equal to the number of turns multiplied by the large side of the tube, as a result this helix has on the one hand a fairly great bukl and on the other hand the winding is not regularly and automatically formed since, as has been emphasized above, the turns are applied against one another by the small sides of the tube and there is a great risk that during the automatic winding under the action of the elastic force, the turns slide in or on one another and thus form an irregular winding.
If to date one has proceeded as has just explained, this is because during winding of the tube on the cylindrical support it is not possible to avoid that the large side of the tube comes naturally to bear against the surface of the support.